NeXTSTEP 3.0

test program:
#include <sys/types.h>
#include <errno.h>
#include <fcntl.h>
#if NORMAL_POSIX_SYSTEM
#include <unistd.h>
#else
/* whence values for lseek(2) */
#define SEEK_SET        0       /* set file offset to offset */
#define SEEK_CUR        1       /* set file offset to current plus offset */
#define SEEK_END        2       /* set file offset to EOF plus offset */
#endif

extern int errno;

void move_it(off_t where, int how)
{
  int error;
  off_t offset;
  static int fd = -1;

  if (fd == -1) {
    if ((fd = open("/vmunix", O_RDONLY)) < 0) {
      perror("open");
      exit(1);
    }
  }
  offset = (off_t)lseek(fd, where, how);
  error  = errno;
  printf("Offset: %d; Errno: %d\n", offset, error);
}

main()
{
  move_it(20, SEEK_SET);
  move_it(-10, SEEK_CUR);
  move_it(-10, SEEK_CUR);
  move_it(-10, SEEK_CUR);

  move_it(0, SEEK_END);
  move_it(-10, SEEK_CUR);
}
-------------------------  results ---------------------
kstailey@leidecker(8)$ ./seektest 
Offset: 20; Errno: 0
Offset: 10; Errno: 0
Offset: 0; Errno: 0
Offset: -10; Errno: 0
Offset: 802493; Errno: 0
Offset: 802483; Errno: 0

It's not an error here either!

Ken